Need help With this C++ Program..Confused..

Okay well i'm having trouble understanding this program ..in which our professor doesn't even explain..I'm so lost..
I hope somebody can help me please..
here's the problem...

I have to write a program in c++ that computes the number of days between two dates using the Julian day number which is the number of days that have elapsed since noon on jan 1, 4713 B.C , so i have to use the julian day number for each date and subtract one from the other.
This algorithm might help.. So given the year (an integer such as 2001), month (an integer from 1 to 12 ), and day ( an integer from 1 through 31), so if month is 1 or 2, then subtract 1 from year and add 12 to month.

If the date comes from the Gregorian calender (later than Oct 15, 1582), then compute an intermediate result with the following formula (otherwise, let intRes1 equal 0):

intRes1 = 2 - year/100+year/400 (integer division)

compute a second intermediate result with the formula

intRes2 = int(365.25 * year)

compute a third intermediate result with the formula

intRes3 = int(30.6001 * (month + 1))

Finally, the Julian day number is computed with the formula
julianDay = intRes1 + intRes2 + intRes3 + day + 1720994.5

So my program should make appropriate use of value-returning functions in solving this problem. integer type long and floating point type double may have to be used. Also it should prompt appropriately for input (the two dates) if it is to be run interactively. also it has to use proper style and comments.
so i have to make up my own test data and be ready to explain rationale behind my choice.
AND thats the situation..I am so stacked and i hope somebody can help me out :confused: ..Well thanks for your time and hopefully i can get this problem solved .. I really appreciate your help and dedication.. Thanks again.

Seems like the crux of your problem's the math.
Specifically, how do I convert ANY date to the Julian calendar day.
Google will provide you with a clear, concise formula to apply to your user's input, that's a formulaic issue.. not programming.

pseudo-code might be

do
{
print Program's purpose
print Enter a date (ddmm [+/-] yyyy)
get Input1
print Enter a date
get Input2
if CheckInputValidity IS INVALID skip rest of loop
convert 2 inputs to julian dates
Do the math.. subtract one from the other
print the results
} while (userInput != Quit)

This may be frustratingly vague.. but the point is to get the exact mathematical formula (I don't have it), and apply it at the appropriate point in the code.
Your instructor may dock you for not error checking the user input, that is.. invalid dates. I'll check back.